Apparatus for grinding flexible workpieces



Oct. 27, 1964 H. E. BALSIGER APPARATUS FOR GRINDING FLEXIBLE WORKPIECES5 Sheets-Sheet 1 Filed Aug, 23, 1962 M G p m i i 5 Z :5. 1: =5 .1. m w m3m p M w fl 2 52 a 7% m E O I @mx /2 m 3 c wfi 1] m 1mm m M mm .m W M m8 8 m M N H m MM 5 6 cm 3 qM WQW l||lk| Q W|-Q\ A'ITDRNEY Oct, 27, 1964H. E. BALSIGER 3,1 84

APPARATUS FOR GRINDING FLEXIBLE WORKPIECES Filed Aug. 23, 1962 5Sheets-Sheet 2 INVENTOR HAROLD tans/5E1 A'ITORN EY Oct. 27, 1964 H. E.BALSIGER 3,1 3,8 4

APPARATUS FOR GRINDING FLEXIBLE WORKPIECES Filed Aug. 23, 1962 5Sheets-Sheet 5 LI L3 JUL INVENTOR mama Lana/gm ATTORNEY Oct. 27, 1964 H.E. BALSIGER 3,153,884

APPARATUS FOR GRINDING FLEXIBLE WORKPIECES Filed Aug. 23, 1962 5Sheets-Sheet 4 INVENTOFZ HAROLD E.BALSIBER ATTORNEY Oct. 27, 1964 H. E.BALSIGER APPARATUS FOR GRINDING FLEXIBLE WORKPIECES 5 Sheets-Sheet 5Filed Aug. 23, 1962 "Ill III IIII l ll l II IIII I III I III I I I]INVENTOR HAROLD E. BALSIGER ATTORNEY United States Patent 3,153,884APPARATUS FOR GRINDMG FLEXIBLE WORKPIECES Harold E. Balsiger,Wayuesboro, Pa, assignor to Landis Tool Company, Waynesboro, Pa. FiledAug. 23, 1962, Ser. No. 219,013 Claims. ((31. 51-165) The presentinvention relates to grinding machines for grinding axially spacedportions of a workpiece, particularly where the workpiece is acrankshaft.

Because of the nature of the crankshaft, certain portions offer moreresistance to the feeding thrust of the grinding wheel in one angularposition than in another. Some bearings may require a difiierentgrinding procedure than others. This may be true whether the portion isa crankpin or a line bearing. For the purpose of illustratin, thisinvention is described in connection with the grinding of line bearingsin both Single and multiple wheel machines.

For example, the center main bearing is subject to variable deflectiondifferent from the end main bearing. Furthermore, the center main orthrust bearing is subject to greater deflection in one angular positionthan in another angular position 90 removed. When the grinding operationbegins, the work is not supported by a work rest until the entiresurface of the bearing has been subjected to the grinding operation.

During this portion of the grinding operation, because the bearing andshaft offer greater resistance to the grinding feed in one angularposition, there will be a greater change in diameter of the bearing inthis position and a lesser change in diameter of the bearing in theangular position in which the shaft offers less resistance to thegrinding feed.

By the time the entire bearing surface has been touched by the grindingwheel, this variable thickness of the unsupported shaft results in ajournal which is substantially elliptical in shape, but symmetrical withthe axis of rotation of the shaft. At this point, according to thepresent invention, the grinding wheel is retracted and a work rest isapplied to the bearing being ground. The wheel is again advanced, butslow down prior to engagement of the work occurs before the wheeladvances far enough to engage the major radius of the elliptical-shapedportions of the workpiece. The grinding operation will then proceed at agrinding rate during which the wheel will grind only the points of majorradius until they have been reduced to the same dimension as the minorradius. The feed may then be continued or reduced to a slower grindingrate which will continue to a point where a feed completion signal willeither retract the grinding wheel, or advance the wheel in a suitablemanner for a precision finishing or sizing operation. Thereafter, thegrinding wheel is retracted either manually or by a timer or by a sizingdevice. On a crankshaft end bearing which is not afiected as much by thevariable stifiness of the shaft, a more or less conventional feed cycleis used.

Where crankshafts are made in large quantities, all the main bearingsmay be ground on a multiple wheel machine using a procedure similar tothat described above in connection with the center main bearing. Whetherthe main bearings are ground one at a time or all at one time, it isimportant that they all rotate about the same axis which is the axis ofrotation of the headstock when they have all been ground to the desiredsize. Otherwise, some or all of the hearings will move in an orbitalpath similar to that of a crankpin. This is accomplished in part byadjusting the rest or rests so that when the shoe is in advancedposition, it is spaced from the axis of 3,153,884 Patented Get. 27, 1964rotation of the headstock by an amount equal to the finished radius ofthe portion which it supports.

Each portion of the shaft will deflect to a difierent extent and themajor diameter of the non-cylindrical contour of the bearings will occurat different angles and by difierent amounts. After the preliminarygrinding operation, the multiple wheel support will be retracted andsteady rests applied to one, two or more of the bearings being ground.When the wheels engage the various portions of the workpiece, they willgrind only on the major diameters regardless of their angular relationto one another until said diameters have been reduced to the samedimension as the minor diameter after which stock removal will occur atsubstantially the same rate on all bearings until final size is reached.

It is, therefore, an object of the present invention to grind a bearingor bearings of a crankshaft not only round, but also concentric with itstrue axis which is also the axis of rotation of the crankshaft. Trueaxis may be defined as the axis about which the bearing will rotate whennot influenced by radial forces including gravity. The true axis is alsothe axis of rotation of the headstock spindle.

Another object is to provide means for grinding the portions of theworkpiece of greater radius before contacting the portions of lesserradius until all portions have been reduced to the same dimension as thelesser radius at which time the workpiece is round and rotating aboutits true axis.

Another object is to provide means for retracting the grinding wheel andwork rest after a preliminary grinding operation to apply a radialsupport to the workpiece and then advance said grinding wheel tocomplete the grinding operation.

Another object is to provide one type of feed cycle for grinding abearing in one longitudinal position on a crankshaft and another type offeed cycle for grinding a bearing in another longitudinal position onsaid crankshaft.

Another object is to provide a feed cycle which will be applicable tothe grinding of a single bearing or to the simultaneous grinding of aplurality of bearings having a common axis of rotation.

Another object is to provide feed control means which are determined bythe longitudinal position of the work carriage.

Another object is to provide means whereby the longitudinal position ofthe work carriage determines the nature of the feed cycle on the portionof the workpiece which is in grinding position.

Another object is to provide means to co-ordinate the operation of thework rest, feed mechanism, and traverse mechanism in accordance with therequirements of a particular feed cycle.

Another object is to provide a machine having at least two automaticgrinding cycles and means for selecting the grinding cycle for eachportion of the workpiece.

FIG. 1 is a front elevation of a grinding machine arranged to grind theline bearings of a crankshaft.

FIG. 2 is a hydraulic circuit.

FIG. 3 is an electrical circuit.

FIG. 4 shows an unground center main bearing of a crankshaft about to besubjected to a preliminary grind ing operation without a work rest.

FIG. 5 shows the workpiece after the preliminary grinding operation FIG.6 shows the workpiece supported by the work rest for the second approachof the grinding wheel.

FIG. 7 shows the workpiece with one portion of the major diameter afterit has passed the grinding wheel.

FIG. 8 shows the workpiece still in process of reducing the majordiameter.

Grinding wheel 30 is. rotatably mounted on grinding.

wheel support 31 which, in turn, is slidably mounted on bed 10. Wheelsupport 31 may be advanced. and retracted manually with relation toworkpiece W by means of hand wheel 40, hand wheel shaft 41, worm gear42, worm wheel43, shaft 44 and worm wheel 45 which engages feed screw46. The relation between feed screw-46 and worm wheel 45 may be eitherthat of a screw and nut or a rack and pinion. One end of feed screw 46is slidably mounted in bed 16 and arranged to engage stop member 47. Theother end of feed screw 46 is mounted in piston 50 which, in turn, isslidably supported in cylinder 51-.

Tail rod 52 extends through the head end of cylinder 51 into a dash potcylinder 55 and is connected to dash pot piston 56 by means of aconventional lost motion arrangement (not shown). Spring 57 in the lowerportion of cylinder 55 serves to reset piston 56 at the end of agrinding cycle. Cylinder 55 is connected to a reservoir 131 by throttlevalve 133 and check valve 134.

Cam ring 60 is mounted on shaft 41 to rotate with hand wheel 40. Cams A,B, C and D on cam ring 60 are arranged to actuate limit switches 6L8,8L5, 171.8 and 18LS as will be described later.

Power means for rotating shaft 41 for a rough grinding operationconsists of pinion 70 on shaft 41 and rack 71 in engagement with pinion70. Shaft 41 may be rotated in a clockwise direction by endwise movementof rack 71 from right to left. Rack 71 is connected to piston 72 incylinder 73.

In order to permit rotation of hand wheel 4%) without being limited bythe rack and pinion, hand wheel 49 is connected to pinion 70 by means ofa clutch arrangement as shown in co-pending application, Serial No.211,937, filed July 16, 1962.

' Operation At the beginning of the cycle after starting the machine,the following circuits are closed:

Limit switch contact 2LS2 to energize relay SCR.

For grinding the center main bearing or thrust bearing, limit switchcontact 19LS1 is closed, completing a circuit to energize relay 80R.

Normally closed relay contact 45CR1 completes a circuit to energizerelay 39CR which is held through relay contact 39CR3 and feed slow downlimit switch 17LS.

A circuit is. completed through normally closed relay contacts 46CR2 and10CR2 to energize work rest reset relay 11CR.

Limitswitch contact 19LS1 is closed by cam 75 on carriage 11, when saidcarriage is in position to place the center main bearing in line withgrinding wheel 35). Since this is the first operation, workpiece W isplaced in the machine with carriage 11 in this position.

Footstock 16 is actuated manually to engage and support workpiece W. Themovement of footstock 16 actuates-footstock limit switch 7L5. tocomplete a circuit to energize relay 6CR.

Relay contact 6CR1 closes to start work drive'motor'ztlwhen'limit'switch ZLS is closed by pressure from cylin der 51. Limitswitch 2LS isshifted to the right'by pres sure from the head end ofcylinder 51 on switch actuating piston 86 in cylinder 87. a

Limit switch 2L8 is shifted in the opposite direction 4 by a smallerpiston 88 in cylinder 89 connected to the rod end of cylinder 51.

The feed movement is started by manually closing wheelbase limit switch3L5 by means of infeed lever and relay contact 39CR1. to complete acircuit to energize fast feed relay 1CR. Relay contact lCRZ is a holdingcontact in the circuit with previously closed relay contact 3QCRZ. Relaycontact 1CR3 closes to energize fast feed solenoid 1. 7

Solenoid 1 shifts fast feed valve 90 to the right to direct fluid underpressure to throttle valve 91 and check valve 92 to the head end of fastfeed cylinder 73. However, no fluid under pressure is available forcylinder 73 until rapid infeed pilot valve 863 is shifted to the rightby pressure from port 93 of rapid feed cylinder 51 at the end of therapid feed movement.

Relay contact 1CR1 completes a circuit which includes normally closedwheel support out limit switch SLS and normally closed feed completionlimit switch contact 6LS1 to energize infeed relay ZCR. Relay contact2CR1 is a holding contact. Relay contact 2CR2 closes to energize infeedsolenoid 2, shifting infeed pilot valve Stl to the right and directingfluid to the right hand end of infeed reversing valve 81 which, in turn,directs fluid under pressure through check valve 82 to the head end ofrapid feed cylinder 51.

Rapid feed piston 59 advances wheel support 31 rapidly toward workpieceW until it picks up dash pot 54 to reduce the rapid feed rate for sidewall grinding as determined by side wall throttle valve 133. Side wallgrinding continues to a positive stop or stop member 47.

At the end of the rapid feed movement, port 93 in cylinder 51 is openedby piston 56) and fluid under pressure is directed to shift pilot valve80 to the right. This movement of valve 80 directs fluid to shiftreversing valve 81 to the right and also to continue on through checkvalve 82 to actuate pressure operated limit switch 2LS. Limit switchcontact 2LS1 closes to energize relay 36CR. Limit switch contact 2LS2opens to deenergize relay SCR.

Relay contact 36CR1 closes to energize workdrive motor relay 6MP andcloses relay contact 6MF1 to start motor 20.

Relay contact 5CR1 opens in the circuit to dash pot relay 7CR which isnot deenergized at this time because it is held by dash pot limit switch16LS and relay contact 7CR1.

When reversing valve 81 is shifted to the right, it directs fluid underpressure from fast feed reset valve 83 through feed stop valve 84 to thehead end of fast feed cylinder 73 as will be described. 7

Advancing wheel support 31 also closes wheel support in limitswitch 3LSto complete a circuit through relay contact 39CR1 to energize fast feedrelay 1CR. Relay contact 1CR1 closes in the circuit to infeed relay 2CR.Relay contact 1CR2 closes in the circuit with relay contact 39CR2 tohold relay ICR. Relay contact 1CR3 closes to energize fast feed solenoid1.

When stop member 47 is reached, pressure'from the head end' of rapidfeed cylinder 51 is applied to the pilot valve 80 which directs fluidunder pressure from fast feed reset valve 83 through feed stop valve 84to fast feed valve'90 which is held in right hand position by previouslyenergized fast feed solenoid 1 and directs fluid through fast feedthrottle valve 91 to the head end of fast feed cylinder 73 to resume theadvance of wheel support'31 by means of fast feed piston 72 for a roughgrinding operation.

Piston 72 operates through a feed hand wheel mechanism until the #1 feedslow down limit switch 17LS is actuated by cam A on hand wheel shaft 41.FIG. 4 shows the workpiece W before the preliminary grinding operation.Limit'switch 17LS opens the circuit through relay holding contact 39CR3to deenergize relay 390R.

Relay contact 39CR1 opens to deenergize fast feed relay 1CR and fastfeed solenoid 1. Valve 90 returns to left hand position, directing fluidunder pressure through slow feed throttle valve 96 and check valve 97 toreduce the rate of movement of fast feed piston '72.

The feed continues at this reduced rate until cam C on shaft 41 actuatesfeed stop limit switch 18LS which closes to complete a circuit whichincludes relay contact 45CR2, normally closed relay contact 43CR2, andrelay contact SCRl, to energize feed stop relay ifiCR. Relay contact46CR1 provides a holding circuit around relay contact 8CR1 and limitswitch 1SLS. Relay contact 4tlCR2 closes to complete a circuit throughrelay contact SCRZ to energize timer clutch relay lTR.

After a round out period, during which the grinding operation continueswithout any feed movement, relay contact lTRl closes to energize relay41CR and slow feed reset timer relay 6TR.

Relay contact 4llCR3 closes to energize feed stop solenoid 2i).

Feed stop valve 84 is shifted to the right to cut off the supply offluid to cylinder 73.

Relay contact 41CR1 closes in the circuit which includes normally closedrelay contact TRl to energize slow feed reset relay 42CR. Relay contact42CR2 closes to energize fast feed reset solenoid 19.

Fast feed reset valve 83 is shifted to the right to direct fluid underpressure to the rod end of cylinder 73, returning piston 72 to startingposition and retracting grinding wheel 34 to the position from whichfast feed starts.

During this portion of the feed cycle, workpiece W has not beensupported by work rest 1% and the work has been permitted to deflectunder the force of the grinding wheel feed. Because of the variablestifiness and consequent variable deflections, workpiece W at this pointis elliptical in shape as shown in FIG. 5 and is still severalthousandths oversize on the minor diameter.

When timer relay 61' R times out, normally closed relay contact 6TR1opens to deenergize slow feed reset relay 420R. Relay contact 6TR2closes in a circuit with previously closed relay contact 41CR2 toenergize relay 43CR. Relay contact 43CR3 closes in a holding circuitwhich includes relay contact 45033. Relay contact 43CR4 closes toenergize relay 46CR. Relay contact 4CR1 is a holding contact. Normallyclosed relay contact 4CR2 opens to deenergize work rest reset relayllCR. Relay contact 11CR2 opens to deenergize work rest reset solenoid5. The work rest is similar in construction to that shown in co-pendingapplication, Serial No. 192,205, filed May 3, 1962.

Work rest reset valve 11% returns to central position, shutting olf thepassage of fluid through the right hand end of said valve to work restcylinder 111 which holds work rest 1% in reset position against wedge112 actuating springs 115. Instead, the fluid under pressure bypassesvalve 110 and is directed to cylinder 111 at a lower pressure determinedby relief valve 113 in the bypass. The pressure of the fluid exerted onwork rest piston 114 is less than that exerted by springs 115 in theopposite direction. Work rest 15%) is fully advanced and the workdeflected to a position where work rest 190 is spaced from the center ofrotation, a distance equal to the radius of a finished workpiece asshown in FIG. 6.

en slow feed reset relay 42CR was energized, relay contact 42CR1completed a circuit to energize relay 440R. Relay contact 44CR2 is aholding contact.

As soon as relay 43CR is energized at the end of the slow feed resetperiod, relay contacts 43CR1 and 44CR1 close to complete a circuit tofast feed relay 1CR, energizing solenoid 1 and shifting fast feed valve90 to the right, directing fluid under pressure through throttle valve91 to the head end of cylinder 73.

Grinding wheel 34 advances at fast feed until it reaches a point spacedfrom work rest 1% slightly more than 6 the major diameter of theelliptical workpiece W as shown in FIG. 6. At this point, the #2 feedslow down limit switch 8L8 is opened to deenergize relay 44CR. Relaycontact 4 5C111 opens to deenergize fast feed relay ICR, deenergizingsolenoid 1.

Fast feed valve returns to the left end position to reduce the feed ratefor the remainder of the grinding operation. During this period, themajor diameter is gradually reduced until it is the same dimension asthe minor diameter as shown in FIG. 9 at which point the work is roundand still oversize.

Also during this period, limit switches 17LS and ISLS are actuated bytheir respective cams, but perform no function.

Limit switch 17LS is rendered inactive as follows:

Relay 39GB. is energized from the beginning through normally closedrelay contact 45CR1 and held through limit switch 1718 and relay contact39CR3.

Rapid feed energizes relay 4-5CR, opening normally closed relay contact45CR1 so that when limit switch 17LS opens to deenergize relay 390R,said relay 39CR cannot be energized again until feed completiondeenergizes relay 45CR, closing normally closed relay contact 45CR1 inrelay 3CR circuit.

Limit switch 17LS is thus inactive during the second advance of fastfeed.

Limit switch 18LS is rendered inactive as follows:

The circuit to feed stop relay 4llCR includes normally closed relaycontact 43CR2 of relay 43CR.

Relay 43CR is energized by timer relay contact 6TR2 and held by relaycontacts 45CR3 and 43CR3.

When timer relay oTR times out, it energizes relay 43CR, openingnormally closed relay contact 43CR2 in the circuit to feed stop relay-lllCR.

Relay 43CR is held by relay contact 45CR3 and relay contact 43CR3, butcannot be deenergized until feed is completed when relay 45CR isdeenergized along with infeed relay 2CR by opening limit switch contact6LS1.

Thus, on the second advance of piston 72, limit switch lSLS is actuatedby one of the cams on shaft 41, but with normally closed relay contact43CR2 open, closing limit switch 18LS does not complete the circuit tostop fast feed. Therefore, fast feed continues until feed completionlimit switch 6L8 is opened by cam B on shaft 41 and both rapid feed andfast feed are retracted.

After the major diameter has been reduced to the same dimension as theminor diameter, the feed movement continues until cam B on shaft 41actuates feed completion limit switch 6L3. Limit switch 6L5 may be usedto start a precision feed, or in this case, stop the grinding operationat the required work diameter. Limit switch contact fiLSl opens todenergize infeed relay ZCR. Limit switch contact 6LS2 closes to energizerelay 9CR.

Relay contact 9CR1 closes to complete a circuit through previouslyclosed relay contact 11CR1 to energize work rest low pressure releaserelay ltlCR, closing relay contact 1%CR3 to energize work rest lowpressure solenoid 4. Relay contact lllCRl is a holding contact.

Work rest reset valve is shifted to the right connecting cylinder 111with exhaust and the full pressure of springs 115 is applied to workrest 1%.

When relay llBCR is energized to energize solenoid 4, normally closedrelay contact ltlCRZ opens to deenergize relay 11CR and solenoid 5.

At the same time, relay contact 2CR2 opens to deenergize infeed solenoid2.

Infeed pilot valve 124? is shifted to the left to direct fluid to theleft hand end of reversing valve 121 which directs fluid to the rod endof cylinder 51 to retract piston 50 and wheel support 31.

After the center main bearing has been ground to size and grinding wheel34 retracted, work rest 10f) remains in engagement with said bearinguntil the end bearings are ground. This is accomplished by preventingenergization of work rest reset relay 11CR and solenoid 5.

The circuit to relay 11CR includes normally closed relay contact 46CR2.Relay 46CR was originally energized by relay contact 43CR4 and heldthrough a circuit having relay contacts 6CR2 and 46CR1.

So long as relay 46CR remains energized, normally closed relay contact46CR2 in the work rest reset circuit will remain open and work rest 100will remain in engagement with the center main bearing for the grindingof the end bearings.

Work rest 190 will not reset until footstock 16 has been retracted torelease workpiece W when footstock limit switch 7LS will open todeenergize relay 6CR.

Relay contact 6CR2 in the holding circuit to relay 46CR will open todeenergize relay 46CR.

Relay contact 46CR2 will then close, energizing work rest reset relayllCR and solenoid to retract work rest 1% to inoperative position.

Carriage 11 is then traversed to place the end bearings in line withgrinding wheel 30. In either of these positions of carriage 11, thrustgrind limit switch 1LS is not actuated. Limit switch contact 19LS1 isopen and limit switch contact 19LS2 is closed.

Rapid feed is initiated in the same manner as described above. However,dash pot rate control valve 136 operates in a different manner than forthe #4 bearing. Limit switch contact 19LS2 completes a circuit throughpreviously closed relay contact 5CR1 to energize dash pot relay 7CR.Relay contact 7CR2 completes a circuit to energize dash pot solenoid 3.

Dash pot rate control valve 130 is shifted to the right andfluiddischarged from cylinder 55 may pass through valve 13% to thethrottle valve 132 which by-passes side wall throttle valve 133 andpermits a more rapid advance of wheel support 31 until the lower sidewalls of the end bearing is reached when solenoid 3 is deenergized.

As wheel support 31 advances, limit switch 16LS is opened by cam 140 onwheel support 31 to deenergize relay 70R and solenoid 3.

Valve 130 then moves to the left, blocking the passage of dash pot fluidto the valve 132 and leaving the side wall throttle valve 133 to controlthe discharge from dash pot 54 to reduce the rapid feed movement to afeed rate suitable for grinding the lower side walls.

The side wall grinding continues until stop member 47 is reached andinfeed pilot valve 80 is shifted to direct fluid under pressure to thehead end of fast feed cylinder 73.

During the operation of the fast feed on either of the end bearings,limit switch SLS is opened by cam D on shaft 41. The function normallyperformed by the opening of limit switch SLS is deenergization of relay44CR and the slowing down of fast feed. However, relay 44CR has alreadybeen deenergized because of carriage 11 being in position to grind oneor the other of the end bearings in one position.

Limit switch contact 19LS1 is opened in the circuit to relay 8CR whichis, therefore, deenergized. Normally open contacts of relay 8CR whichare necessary to energize relay 44CR thus prevent relay 440R from beingenergized.

When limit switch SLS is rendered inactive, the fast feed movementcontinues at the same rate until feed completion limit switch 6LS isopened, either to deenergize infeed relay ZCR and retract grinding wheel30, or to actuate through a circuit (not shown) to initiate a precisionfinishing feed.

Rotation of the manual feed mechanism by piston 72 in cylinder 73continues until cam B on shaft 41 actuates limit switch contact 6LS1 toopen the circuit to infeed relay 2CR and deenergizing infeed solenoid 2to retract wheel support 31 through piston 72 and cylinder 73, and atthe same time, to retract piston 72 and associated feed mechanism inpreparation for the grinding of another workpiece W.

Resetting piston 72 must be accomplished at different times underdifferent conditions. At the end of the preliminary grinding operationon the center main hearing, fast feed reset solenoid 19 is energized toshift fast feed reset valve 83 to direct machine pressure to the rod endof cylinder 73. Exhaust from the head end of cylinder 73 may returnthrough check valve 78 to reset valve 83 which is in a position todirect said exhaust fluid through reversing valve 121 which is in theright hand position and will direct said fluid to the main exhaustpassage.

At other times, when solenoid 19 is deenergized, valve 121 which directsfluid under pressure to the rod end of cylinder 51 also directs fluidthrough valve 83 in the left hand position, and connects the conduitleading from reversing valve 121 with line 94 to the rod end of cylinder73. When reset in this manner, the exhaust from the head end of cylinder73 may not return through check valve 73 to valve 73 because said valveis in position to direct machine pressure against check valve 78. Theexhaust fluid must, therefore, be directed through check valve 79 toreversing valve 121 which is in the right hand or reset position anddirects exhaust fluid from check valve 7 9 to the main exhaust line.

When reversing valve 121 is in left hand position, check valve 7?prevents fluid under pressure from reaching the right hand end of fastfeed cylinder 73 uncontrolled instead of through fast feed valve 90.

When footstock 16 is retracted after grinding the two end bearings, toremove workpiece W from the machine, limit switch 7LS is opened todeenergize relay 6CR. Relay contact 6CR2 opens in the holding circuit todeenergize relay 460R.

Normally closed relay contact 46CR2 closes to energize work rest resetrelay llCR and solenoid 5.

Normally closed relay contact 11CR1 opens in the circuit to work restlow pressure release relay 10CR, deenergizing solenoid 4.

Work rest reset valve moves to the left, connecting cylinder 111 withfull pump pressure, resetting wedge 32 against springs 115 to permitretraction of work rest When it is desired to traverse carriage 11 fromthe position for grinding the center main bearing to a position forgrinding either. of the end bearings, traverse control lever is shiftedto actuate limit switch 9LS in a circuit which includes limit'switch15LS which is closed only when wheel support 31 is in retracted positionwhere grinding wheel 30 will not interfere with the traverse movement.

Traverse start relay 22CR is energized and relay contact 22CR1 closes toenergize traverse start solenoid 11. Traverse start valve 141 is shiftedto the right to direct fluid under pressure to shift pressure operatedtraverse start valve 142 to direct fluid under pressure to traversereversing valve 143 from which said fluid is directed alternately toopposite ends of traverse cylinder 144 to shift "carriage 11f I claim:

1. In a grinding machine for grinding axially spaced portions of aworkpiece in which the stiffness of the workpiece varies from portion toportion, a bed, a grinding wheel support slidably mounted on said bed, agrinding wheel rotatably mounted on said wheel support, a work carriageslidably mounted on said bed, means on said work carriage for rotatablysupporting a workpiece, means for effecting relative transverse andlongitudinal movements of said wheel support and said work carriage, aplurality of limit switches adapted to be actuated by said transversemoving means, a limit switch on said bed, and means on said workcarriage for actuating said bed mounted limit switch, said bed mountedlimit switch being operable to render certain of said first mentionedlimit switches active to control said transverse moving means, said bedmounted limit switch being operable in another position of said workcarriage to render others of said 9 first mentioned limit switchesactive to control said transverse moving means.

2. In a g inding machine for grinding axially spaced portions of aworkpiece in which the stifiness of the workpiece varies from portion toportion, and in a given portion, from one angular position to another, abed, a grinding wheel support on said bed, a grinding wheel on saidwheel support, a work carriage on said bed, means for effecting relativetransverse and longitudinal movements of said wheel support and saidwork carriage, a limit switch on said bed corresponding to one of saidaxially spaced portions of the workpiece and adapted to be actuated whensaid work carriage places that particular portion of the workpieceopposite said grinding wheel to initiate a feed cycle different fromthat used on other portions of said workpiece.

3. In a grinding machine for grinding axially spaced portions of aworkpiece in which the stiffness of the workpiece varies from portion toportion, a bed, a grinding wheel support on said bed, a grinding wheelrotatably mounted on said wheel support, a work carriage on said bed,means for effecting relative transverse and longitudinal movements ofsaid work carriage, a plurality of limit switches adapted to be actuatedby said transverse moving means, a limit switch on said bedcorresponding to one of said axially spaced portions of a workpiece,said bed mounted limit switch being operable when the correspondingportion of the workpiece is in grinding position to co-act with one ormore of the limit switches actuated by said transverse moving means tocontrol a grinding feed cycle adapted to the requirements of the portionof the workpiece to be ground.

4. In a grinding achine for grinding axially spaced portions of aworkpiece in which the stiffness of the workpiece varies from portion toportion, and in a given portion, from one angular position to another, abed, a grinding wheel support on sm'd bed, a grinding wheel rotatablymounted on said wheel support, a work carriage on said bed, means foreffecting relative transverse and longitudinal movements of said wheelsupport and said work carriage, a limit switch on said bed correspondingto one of said axially spaced portions of the workpiece, means on saidwork carriage for actuating said limit switch when said work carriageplaces that particular portion of the workpiece opposite said grindingwheel to initiate a feed cycle peculiar to that portion of saidworkpiece, comprising feed means for advancing and retracting said wheelsupport, a plurality of limit switches arranged adjacent said feedmeans, and a plurality of cams movable with said feed means forsuccessively actuating certain of said limit switches to control theoperation of said feed means.

5. In a grinding machine for grinding axially spaced portions of aworkpiece in which the stiffness of a workpiece in a given portionvaries from one angular position to another, a bed, a grinding wheelsupport movable on said bed, a grinding wheel on said wheel support,means on said bed for rotatably supporting a workpiece, means for movingsaid work support longitudinally on said bed, means for effecting afeeding movement of said wheel support toward and from said worksupport, a limit switch, means on said work support corresponding to oneof said axially spaced portions of the workpiece for actuating saidlimit switch, means responsive to said limit switch when said workcarriage places a particular portion of the workpiece opposite saidgrinding wheel to advance said grinding wheel for a preliminary grindingoperation during which said workpiece is deflected by a difierent amountin difierent angular positions with a resultant elliptical or othernon-cylindrical contour, control means to retract said grinding wheelafter a predetermined advance, a work rest movable into and out ofoperative relation with said workpiece, means to repeat said feedmovement with said work rest holding said workpiece in a predeterminedposition, control means operable before said wheel advances far enoughto engage the major radius of the workpiece, to reduce the rate of saidfeed and then to gradually reduce the major radius of the workpiece bygrinding to the same dimension as the minor radius of the workpiece toprovide a work surface con centric with the true axis of the workpiece,and control means operable when said round workpiece has been ground tothe desired size for retracting said grinding wheel.

6. In a grinding machine for grinding axially spaced portions of aworkpiece in which the stiffness of a workpiece in a given portionvaries from one angular position to another, a bed, a grinding wheelsupport movable on said bed, a grinding wheel rotatably mounted on saidwheel support, means on said bed for rotatably supporting a workpiece,means for moving said work support longitudinally on said bed, means forefiecting a feeding movement of said wheel support toward and from saidWork support, a limit switch, means on said work support correspondingto one of said axially spaced portions of the workpiece for actuatingsaid limit switch, means responsive to said limit switch when said workcarriage places a particular portion of the workpiece opposite saidgrinding wheel to advance said grinding wheel for a preliminary grindingoperation during which said workpiece is deflected by a difierent amountin different angular positions with a resultant elliptical or othernon-cylindrical contour, control means to retract said grinding wheelafter a predetermined advance, a work rest movable into and out ofoperative relation with said workpiece, means to repeat said feedmovement with said work rest spaced from the axis of rotation of saidworkpiece a distance equal to the radius of the finished workpiece andholding said workpiece in a predetermined position, control meansoperable before said grinding wheel advances far enough to engage themajor radius of the workpiece, to reduce the rate of said feed and thento gradually reduce the major radius of the workpiece by grinding to thesame dimension as the minor radius of the workpiece to provide a worksurface concentric with the true axis of the workpiece, and controlmeans operable when said round workpiece has been ground to the desiredsize for retracting said grinding wheel.

7. In a grinding machine for grinding axially spaced portions of aworkpiece, a bed, a grinding wheel support on said bed, a grinding wheelrotatably mounted on said wheel support, a work carriage on said bed,means for eifecting relative transverse and longitudinal movements ofsaid wheel support and said work carriage, feed means for advancing saidwheel support for a preliminary grind ing operation, a pair of limitswitches operated sequentially by said feed means for controlling saidpreliminary grinding operation, one of said limit switches beingoperable to retract said feed means, means to again advance said feedmeans, a second pair of limit switches sequentially operable to controlsaid second teed movement, and means for making one of said second pairof limit switches inactive when said work carriage is in anotherlongitudinal position.

8. In a grinding machine for grinding axially spaced portions of aworkpiece in which the stifiness of the workpiece varies in a givenportion from one angular position to another, a bed, a grinding wheelsupport movable on said bed, a grinding wheel rotatably mounted on saidwheel support, a work support on said bed, means for feeding said wheelsupport to efiect a preliminary grinding operation on one of saidportions, means to retract said grind ing wheel when it has advanced toa predetermined position, means to again actuate said feeding means tofeed said grinding wheel to a less advanced position than for saidpreliminary grinding operation, means to advance a work rest to engageand support a workpiece in position to rotate about its true axis, andmeans to retract said grinding wheel after it has advanced to anotherpredetermined position.

9. In a grinding machine for grinding axially spaced portions of aworkpiece in which the stillness of the work, piece varies from portionto portion and in a given portion, from one angular position to another,a bed, a work support on said bed, means for rotatably supporting aworkpiece on said work support, a grinding wheel support slidablymounted on said bed for movement toward and from said work support, oneor more grinding wheels rotatably mounted on said wheel support, meansfor feeding said wheel support toward and from said 'work support toeffect a preliminary grinding operation on one or more of said portions,the resulting contours of said portions being such that each has a minorand a major diameter, means to retract said wheel support when it hasadvanced to a predetermined position, work rests for one or moreselected portions of a workpiece, and means operable while said wheelsupport is retracted to advance each of said work rests to engage andsupport each portion of a workpiece in a position to rotate about itstrue axis, means to again feed said wheel supportto a position toconform to the major diameter of the workpiece, means to continue thefeeding movement of said wheel support to gradually reduce the majordiameter of each portion of a workpiece until it has the same dimensionas the minor diameter, and means to retract said Wheel support after allportions of said workpiece have been ground to the desired diameter.

12 h 10. In a grinding machine for grinding a workpiece in which thestiffness of the workpiece varies in a given portion from one angularposition to another, a bed, a grinding wheel support movable on saidbed, a grinding wheel rotatably mounted on said wheel support, a worksupport on said bed, means for feeding said wheel support to effect apreliminary grinding operation on said workpiece, means to retract saidgrinding Wheel when it has advanced to a predetermined position, meansto again actuate said feeding means to feed said grinding wheel to aless advanced position than for said preliminary grinding operation,means to advance a work rest to engage and support a workpiece inposition to rotate about its true axis, and means to retract saidgrinding wheel after it has advanced to another predetermined position.7

References Cited'in the file of this patent UNITED STATES PATENTS2,142,050 Garside et al. Dec. 27, 1938 2,471,706 Spongberg et al May 31,1949 2,638,719 Balsiger et a1 May 19 1953 2,780,895 Silven et al. Feb.12, 1957 3,067,551 Maginnis Dec. 11 1962 3,071,904 Delafontaine Jan. 8,1963

1. IN A GRINDING MACHINE FOR GRINDING AXIALLY SPACED PORTIONS OF AWORKPIECE IN WHICH THE STIFFNESS OF THE WORKPIECE VARIES FROM PORTION TOPORTION, A BED, A GRINDING WHEEL SUPPORT SLIDABLY MOUNTED ON SAID BED, AGRINDING WHEEL ROTATABLY MOUNTED ON SAID WHEEL SUPPORT, A WORK CARRIAGESLIDABLY MOUNTED ON SAID BED, MEANS ON SAID WORK CARRIAGE FOR ROTATABLYSUPPORTING A WORKPIECE, MEANS FOR EFFECTING RELATIVE TRANSVERSE ANDLONGITUDINAL MOVEMENTS OF SAID WHEEL SUPPORT AND SAID WORK CARRIAGE, APLURALITY OF LIMIT SWITCHES ADAPTED TO BE ACTUATED BY SAID TRANSVERSEMOVING MEANS, A LIMIT SWITCH ON SAID BED, AND